Re: {Chrysler 300} Two Circuit Master Cylinders 60-61

I own a 65 Corvette with manual disks on all 4. At 3,100 pounds pedal effort is firm but not where you want assist. Few cars were sold with non-assisted disks, the Corvette, Maverick, Mustang all light weight cars were. As you know, no servo action with disks so pedal effort is high, assist is required on a heavy car.

My experiences with F front disk brake conversion seem to mirror yours. I have it where I'll live with it. But I'd go back to front drums and the stock system if it wasn't...to late for that now.

-----Original Message-----
From: "John Grady" <jkg@xxxxxxxxxxxxxxxxx>
Sent: Tuesday, February 8, 2022 10:31am
To: "Bob Jasinski" <rpjasin@xxxxxxxxxxx>, "chrysler 300 club" <chrysler-300-club-international@xxxxxxxxxxxxxxxx>
Cc: dplotkin@xxxxxxxxxxxxxxxxxxx, "'AWRDOC' via Chrysler 300 Club International" <chrysler-300-club-international@xxxxxxxxxxxxxxxx>
Subject: Re: {Chrysler 300} Two Circuit Master Cylinders 60-61

Hi ,

agree with below , — but do not eliminate the gap at pushrod . Things change with temp —if it blocks even partially (the internal fill port ) you then cannot pump any more fluid in from the reservoir ; brakes will work only one stroke , that’s it . you do not know that is the situation either . needs .010 or more gap for sure . Not worth risk to push on that spec .

Big surprise for you — if a seal failure in the wheel , and suddenly pumping does nothing . Pedal on floor . Dual master and all .

In line with below , the last few cars I have used corvette masters , but you have to redrill firewall and plates to two larger bolts .

They are available in three bores and all combos of drum and disc . Easily done when car is stripped , fits under the booster nicely but they are long . May hit ram

However , lack of master cc capacity is not the root problem ..:If you up the cc with larger bore , you get less braking vs push on pedal , that may be ok , cuts excessive travel . But no free lunch . Been there .

Another thing I knew but ignored and it really hurt me , and just like Danny says with dot 5 ,— I blamed 5 for long travel , compressibility soft pedal etc in a AAJ disc front F conversion , F drum rears . Bled 10 times . No change. Mopar master . Purposely the car had been set up with the correct pedal ratio ( from a dodge) and MC mount height / bore for manual brakes . ( both must change, never change to manual without relocating master vertically ) . Result of disc conversion was not much brake ( imho ) as defined by stopping power . Very disappointing -/ and long pedal travel too . I love manual brakes , not the point .Better put , I loved manual drums ...

Gave me pause , disc and manual not so good ? But what about Corvettes ?

Anyway after a great deal of work and matching frustration , including blocking the front hydraulic system , then back system then hoses then measuring caliper deflection movement while seated at high pressure etc ( we are talking months ) , -after all this , it pointed to rears as 75% of the lost motion . But some in disc front too . Yet same caliper on a GM car are just

terrific . Made no sense .

I talked a lot to Master Power Brakes too , good guys , recognized experts , but they had no real insights beyond the obvious( good web site) ;They got me all into GM “anti knock back “ calipers , a waste of time red herring .

But that is actually a huge problem with Wilwood calipers , with live pucks on both sides . In a race the pedal can suddenly drop a lot , as the rotor movement knocks the disc piston back into its cylinder on corners as disc moves in and out . On both sides of the rotor -Nice .

So I just kept driving ; I know, like Roger does , Gm calipers are good ..

guess what !!! after 1500 miles brakes were great .

This has bit me hard so many times now I feel really stupid . Our brakes are often useless for first 1500 miles till the shoes bed in , and center ( period!!!imho) and I think something like this happens to disc puck too . It does not touch right day one , I think , maybe only a small portion of shoe surfaces -in drum especially - are really working . . So any judging brakes just after assembly and first trial drive will lead you down a frustrating 1000 mile garden path . This also means a lot of drum adjustment and falling of pedal is normal in that first few thousand .

Just sayin ! I have seen this 7-8 times now.

I think 300 shoes physically deform above an initial small contact patch ( which being small, = little braking) — if not in absolutely perfect total 360 contact , the deformation acts just like air = a springiness in your system . If there is fault in this design it is requiring a perfect shoe fit . Does not happen at assembly ever after 60 years . Especially with all new parts . Keep your old shoes and drums leave them alone .

And discs need to seat too .

Self energizing action of drums matters a lot , —-once settled in — our drum brakes may be better “feeling “ than any disc , especially unboosted , for the first stop (of multiples, before hot) — that is for sure. And we are not racing the car .The Kieckhoffer (sp?) NASCAR B had no problems , -so, if you don’t agree that “ total contact “ brakes are ok as designed , think about that ... Looking back , our brakes won 100’s of races at Nascar , says our “ bad mopar brake” problems are all self inflicted .and I admit to that . I know a lot less now than I used to.

just info ..

ps , as mentioned before , sudden locking after storage pre 62 is internal rust on drum , typically self energizes erratically like crazy . Often one side . Back up fast apply brakes , 4/5 times , before pulling it apart !! fixed . Nothing is wrong !
John g

Sent from my iPhone not by choice

On 7 Feb 2022, at 5:47 pm, Bob Jasinski <rpjasin@xxxxxxxxxxx> wrote:

Thanks Danny, very informative!

Bob J

From: chrysler-300-club-international@xxxxxxxxxxxxxxxx <chrysler-300-club-international@xxxxxxxxxxxxxxxx> On Behalf Of dplotkin@xxxxxxxxxxxxxxxxxxx
Sent: Monday, February 7, 2022 2:33 PM
To: 'AWRDOC' via Chrysler 300 Club International <chrysler-300-club-international@xxxxxxxxxxxxxxxx>
Subject: {Chrysler 300} Two Circuit Master Cylinders 60-61

Further to the brake master conversation, the 2 pot master to fit a 68 New Yorker with drum brakes has a 1" bore and is available at O'Reilly, has a nut in the center and is low and short enough to fit below the booster on a 60-61 RAM equipped Mopar.

This master also works with GM B body front disk brake calipers and Mopar B body rear cylinders as I have on my 61 Savoy with Ram Induction.

But when I tried that master on my F, with GM front calipers but the stock F 1-1/8 " rear cylinder bore, no dice. Could not get rear brakes to operate, too much pedal not enough juice. My use of DOT 5 is likely operative but I insist on it. To make sure defective parts were not involved I tried two masters and two sets of calipers. We bled until we bled.

Finally, and in consultation with AAJ brakes I bought a 1970 Imperial master, had my machine shop cut it down .700", drilled and tapped two screw holes to replace the bail, knocked the two teats on top of the lid down in a press for clearance, and walah! Brakes!

Sort of. I had to put a little preload on the pedal rod, not enough to cover the compensator port but a tad to make it work right. Its pretty darn good too, but I would have left the drums on if it had been my decision

I've attached some photos and a file on Mopar master cylinders. Remember that bore size and pedal travel/effort are related. Small bore = longer travel but less effort, larger bore = less travel, more effort.

Think out your brake project, don't throw parts at it.

Danny Plotkin

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